Organizations are generating and accumulating increasingly large amounts of electronic data that needs to be properly retained and promptly accessible when needed. Given the large volume of data involved and the extended retention period for much of this data, it is critical that a storage system be cost-effective and energy-efficient. In addition, the storage system should also be resilient to partial failures of the system. In addition, the storage system should allow for incremental growth in capacity, facilitate upgrades to the system, and migration of data to new storage devices.